A US man who hacked into the email accounts of celebrities including Scarlett Johansson and Mila Kunis and later leaked their nude photos has been sentenced to 10 years in prison.

Former office clerk Christopher Chaney, who claims he was "addicted" to spying on celebrities' private lives, leaked naked pictures of the shlebs to two celebrity gossip websites and a hacker.

Scarlett Johanssen said in a video statement to the court that the leaked images, which were selfies she snapped while topless, were taken for her then-husband Ryan Reynolds, and said she had been "truly humiliated and embarrassed" when they turned up online.

Prosecutors said Chaney had illegally accessed the email accounts of more than 50 celebrities between November 2010 and October 2011, including an account belonging to singer Christina Aguilera. He was charged with 28 counts relating to hacking and made a plea deal for cases in nine felony courts, Reuters reported.

He was also ordered to pay $66,179 in restitution to victims.

"I don't know what else to say except I'm sorry," Chaney said during his sentencing. "This will never happen again."

Chaney was arrested after an FBI investigation dubbed "Operation Hackerazzi" in October 2011. After his arrest, he told a Florida television station that he had started hacking into celebrity email accounts out of curiosity and then became "addicted".

"I was almost relieved months ago when they came in and took my computer ... because I didn't know how to stop," he said.

Prosecutors alleged that Chaney had also stalked two Florida women online, one since 1999 when she was 13 years old. ®